Патент USA US3088901код для вставки
May 7, 1963 F. e. FOOTE ETAL 3,088,891 FUEL ELEMENTS FOR NEUTRONIC REACTORS Filed March 4, 1949 3 Sheets-Sheet 1 May 7, 1963 F. G. FOOTE Em 3,088,891 FUEL ELEMENTS FOR NEUTRONIC REACTORS Filed March 4. 1949 ' 5 Sheets-Sheet 2 INVENTOR5-' BY f'r'azz/Z’ ¢Foote May 7, 1963 F. G. FOOTE ETAL 3,088,891 FUEL ELEMENTS FOR NEUTRONIC REACTORS Filed. March 4, 1949 3 Sheets-Sheet 3 4 1:13;? Z0 Z4 3,988,891 Patented May 7, 1963 2 3,088,891 FUEL ELEMENTS FOR NEUTRONIC REACTORS Frank G. Foote, Chicago, 111., and Eric R. Jette, Los Alamos, N. Mere, assignors to the United States of America as represented by the United States Atomic of development of defects in the bonding so provided, “hot spots” will develop at the surface of the ?ssionable material at points where the heat transfer is inadequate, and the ?ssionable material may melt or suffer undesir able chemical reactions with the bonding material or the jacket. The provision of a suitable bond for maintaining heat transfer between the ?ssionable material and the jacket, and thus between the ?ssionable material and, the coolant, has been one of the major problems in the de This invention relates to neutronic reactors. More 10 sign and construction of neutronic reactors. Accordingly, it is the principal object of the present speci?cally the invention relates to an improved fuel ele Energy Commission Filed Mar. 4, 1949, Ser. No. ‘79,703 2 Claims. (Cl. 204-154.2) invention to provide an improved form of bond or heat transfer medium between a body of ?ssionable material and a jacket or can enclosing such material, for use in chain reaction occurs by ?ssion of a thermally ?ssionable material (i.e. a material containing an isotope ?ssionable 15 a neutronic reactor. The invention will best be under stood by description of a single embodiment thereof as by thermal neutrons). In the so-called “thermal” reactor, ment structure for neutronic reactors. As is by now well known, in a neutronic reactor, a the chain reaction is sustained by ?ssion of the thermally ?ssionable isotopic content of the thermally ?ssionable material by thermal neutrons, i.e. neutrons having no energy other than that which they possess by reason of temperature. In such reactors, there is incorporated a moderator material in which the ?ssionable material is dispersed, either homogeneously or as aggregated bodies. In the “fast” reactor, little or no moderator is incorpo illustrated by the attached drawing, in which: FIG. 1 is a plan view, partially broken away, of a reactor fuel element embodying the invention; FIG. 2 is a side elevation, partially broken away, of the fuel element of FIG. 1; FIG. 3 is a cross-sectional view of the fuel element of FIG. 1 illustrating the placing of the fuel element in a coolant channel of a neutronic reactor; FIG. 4 is a fragmentary cross~sectional view of a neu rated, and the chain reaction is maintained by ?ssion 25 tronic reactor incorporating the fuel element of FIG. 1; caused by “fast” neutrons, i.e. neutrons of high energy. Reactors may also be so designed that the bulk of the nuclear ?ssions are produced by neutrons of intermediate FIG. 5 is a plan section of the reactor of FIG. 4 taken along the line 5-5 in the direction indicated by arrows; and energies. P16. 6 is a vertical sectional view taken along the line It will be understood that the present invention is not 30 6—6 of FIG. 4. concerned with the nuclear phenomena by which a chain The jacketed fuel element 8 of FIGS. 1, 2, and 3 is a reaction is obtained, nor with such design features as ?at rectangular slab 11) of natural or isotopically en critical dimensions, purity, choice of moderator or ?ssion riched uranium or plutonium encased in a jacket 12 of able material, or the pattern or “geometry” in which the ?ssionable material is disposed in order to produce the 35 aluminum or stainless steel. The jacket 12 is formed chain reaction. Such criteria for the operativeness of a of an upper recessed member 14 and a lower recessed member 16, both of which have ?anges 18, the ?anges 18 being super-imposed and being welded all around the in the neutronic reactor art, and are disclosed in the co perimeter to form a pressure-tight jacket for the uranium pending application of Enrico Fermi and Leo Szilard, Serial No. 568,904, ?led December 19, 1944, now Patent 40 body 10. The jacket 12 is provided with longitudinal ribs 21) on the upper and lower surfaces. All voids within No. 2,708,656, issued on May 17, 1955. the jacket 12 left unoccupied by the ?ssionable material Neutronic reactors are commonly cooled by heat ex neutronic reactor are now well known to persons skilled change between the ?ssionable material and a ?uid cool 10 are ?lled with a thermally conductive liquid 26. The ?lling and sealing may be accomplished by ?rst welding cooled. In order that the ?ssionable material not ‘be 45 three edges of the jacket 12, then inserting a ?ne needle through the unwelded edge with the unwelded edge placed chemically affected by the coolant, and in order that the uppermost, ?lling the jacket 12 under pressure slightly coolant not become contaminated with ?ssionable ma greater than atmospheric pressure, and ?nally completing terial or with highly radioactive ?ssion products, the ?s the closure by welding. Preferably precautions are taken sionable material which is usually called a slug is usually ant, which is ?owed through the reactor and externally insulated from ?owing coolant by a barrier such as a jacket or can. The jacket or can must be of a thermally conductive material in order to preserve a high rate of heat exchange between the ?ssionable material and the to avoid the entrapment of air within the jacket 12. Preferably the liquid which establishes thermal contact between the uranium body It) and the jacket 12 is a thermally conducting metal having a melting point lower than 100° C. It is also desirable that the bonding mate must have a relatively low cross-section for capture of 55 rial have low neutron adsorption characteristics. Exem plary of such metals are sodium and sodium-potassium neutrons, in order that the chain reaction not be pre alloys. vented by high neutron absorption in non-?ssionable ma FIGS. 4, 5 and 6 illustrate schematically a neutronic terials. Aluminum and stainless steel are commonly em reactor incorporating the fuel element described above. ployed as such jacketing materials. Neither the choice The active portion of the reactor is enclosed within a of jacketing material, nor the maximum thickness or cylindrical pressure shell 30 having end walls 32. The minimum purity thereof required in order that the chain pressure shell 30 is surrounded by a neutron re?ector 34, reaction may be maintained constitutes any portion of for example of graphite. Within the shell 31) is a mass the present invention, being determinable in accordance 24- of a moderator material such as beryllium. Coolant with criteria set forth in the copending application re ferred to above, and now well known in the neutronic re 55 ?ow and fuel passages 22, rectangular in cross section, extend through the moderator mass 24. The jacketed actor art. fuel members 8 are placed within the passages 22, as Where the ?ssionable material is incorporated in the shown in detail in FIG. 3. The end walls 32 of the pres jacket and operation at any considerable level of power sure shell 30 are apertured to receive rectangular pipes (heat generation in the ?ssionable material) is required, it is necessary that the ?ssionable material be “bonded” 70 36 which form inlet and outlet passages to the respective coolant and fuel channels 22. The coolant pipes 36 are to the jacket in order that uniform heat transfer be main joined to the end Walls 32 of the shell 30 in pressure tained. In the absence of such bonding, or in the event coolant. In addition the material of the jacket or can 3,088,891 4 3 tight fashion, as by welding. At the outlet end of each channel 22 is positioned a vertical pin 38 which retains the jacketed fuel member 8 within the shell 30 against the pressure of the coolant. *It will be understood that the coolant is not illustrated in the drawing, the choice of coolant, like the choice of ?ssionable material, jacketing material, dimensions, and critical size being by now well within the skill of the art. As is likewise indicated schematically in the drawing, such fuel elements, which may readily be designed. A single embodiment has herein been illustrated and described in accordance with the patent statutes. How ever the extent of patent protection to be accorded the invention should be determined not by the particular embodiment herein disclosed, but by the claims hereto appended. ~What is claimed is: 1. As an article of manufacture, a slug jacket con there is provided a control rod 40 of a neutron absorbing 10 taining a unitary core of ?ssionable material and a material, such as boron, cadmium, or compounds thereof, which protrudes into the shell 30 and which may be inserted or withdrawn to reduce or increase the reactivity of the reactor. ‘The control rod 40 operates in a well 42 which enters the shell 30 through a pressure-tight welded seal at 44. The control rod 40 may be cooled by the ?owing of helium in the well 42. By incorporation of the liquid metal bond 26 there are eliminated the problems which arise with the bonding agents heretofore employed. The lique?able metal bond 20 is self-healing and effectively acts to prevent the develop ment of faulty portions of the thermal bonding between the body of ?ssionable material 10 and the jacket 12. Although, as stated above, the metal of the bond 26 preferably has a melting point below 100° C., it will 25 be understood that it is within the purview of the inven tion to employ a metal of higher melting point and to lique?able metal bond of a metal of the group consisting of sodium and sodium-potassium alloys. 2. As an article of manufacture, a slug jacket con taining a unitary core of thermally ?ssionable material surrounded by a lique?able metal bond of a sodium potassium alloy. References Cited in the ?le of this patent UNITED STATES PATENTS 1,202,162 Clay _______________ __ Oct. 24, 1916 233,011 861,390 Switzerland ___________ __ Oct. 2, 1944 France ______________ __ Feb. 7, 1941 FOREIGN PATENTS OTHER REFERENCES Smyth: A General Account of the Development of operate the neutronic reactor at a temperature above Method of Using Atomic Energy for Military Purposes the melting point of the material of the bond 21’: but below the melting point of the ?ssionable body 10 or the jacket 12. Persons skilled in the art will readily understand that the embodiment of the invention herein illustrated is only Under the Auspiccs of the United States Government, 1940-1945, pp. 84 and 106. Publ. Aug. 11-12, 1945, U.S. Government Printing Office. Kelly et al.: Phy. Rev. 73, 11-35-9 (1948). one of a vast number of ‘fuel elements employing the Liquid-Metals Handbook, Navexos, p. 733, June 1, 1950, Atomic Energy Commission-Department of the liquid bond of the invention, and of reactors employing 35 Navy, ?rst edition, pp. 46, 47.